The present invention relates to the packaging of loose solid substances, whether foodstuffs or pharmaceutical products, and in particular relates to a device for automatically packaging tea, chamomile, and/or similar herbal products for infusion in bags made of filter paper.
In general product packaging technology, there is an established tendency to keep reducing the quantity of material used to make the product packet, while the actual amount of product contained in the packet remains unchanged. In the tea sector, this means a constant search for, on one hand, new bag shapes, whose production requires reduced quantities of filter paper to contain the same dose; and on the other hand, a search for new technical solutions and production devices which allow an increase in the amount of the product which can be contained in a bag with a precise given shape and dimensions.
The sector for obtaining packets which allow greater economy with materials, in particular, filter paper, includes a machine designed by the Applicant (see patent IT-1.279.697) which forms tea bags in a succession of stages which envisage: dosing the tea on a single continuous web of filter paper using a special dosing wheel whose edge makes direct contact with the web; folding the continuous web of filter paper over itself lengthways; overlapping the folded edges of the web in such a way that the successive doses of tea contained inside it are wrapped up; sealing the overlapping edges of the web, around the doses; and finally, cutting the web into sections corresponding to the individual bags of the product. The dosing wheel allows the doses of tea to be kept relatively compact around the depositing zone and the use of a single web of material, folded over itself, allows a reduction in the quantity of paper used.
The tea bags made using this machine, therefore, have quite a low amount of packaging material per product unit packaged. However, this already advantageous aspect must be further modified in the continued effort to reduce the amount of packaging materials used.
Moreover, this machine, like all known machines which heat-seal filter paper, has the disadvantage that it is impossible to rule out the possibility that the particles of tea may move away from the zone where the dose is deposited, due to machine vibrations, and may then remain between the sealed edges of the bags, on one hand causing disadvantages to bag feed during their formation, and on the other hand sometimes rendering the appearance of the finished bag unsuitable.
The main aim of the present invention is to allow an increase in the amount of product which can be contained in a bag with a preset capacity.
A further aim of the present invention is to prevent particles of the product from moving away from the zone in which the doses are deposited and reaching the zones to be heat-sealed.
Accordingly, the present invention achieves these aims by providing a device for compacting, on a first conveyor belt, made of a material which is permeable to air, in particular consisting of a web of filter paper which moves with a linear velocity V, a solid substance, consisting of loose particles, deposited in doses at regular intervals by dosing means which are synchronized with the linear velocity V of the first conveyor belt. The device comprises a second conveyor belt, which moves at the same speed as the first and is located below the latter. The second conveyor has through-holes along its length, at intervals which correspond with the intervals at which the doses of the substance are deposited on the first belt; and vacuum means which are in continuous communication with the holes in the second belt in such a way that, through the first belt, they exert a suction on the doses of the substance which compacts the doses and keeps the particles packed tightly together and in contact with the first belt below them.
Thanks to the fact that the doses are held on the first conveyor belt, that is to say, the web of filter paper of which it consists, the device allows an increase in the operating speed of the packaging machines to which it is fitted.
In fact, this method of holding the tea in a compact form allows the packaging machine to be pushed to its highest possible mechanical operating speeds, without fear of disadvantages or deterioration in the quality of the product which could be caused by the corresponding increase in the level of machine vibrations.
The low level vacuum required to hold the doses of tea in place also means that the above-mentioned advantages can be obtained with a small amount of energy and relatively low costs for production of the device.